--- title: Interharmonics and RMS Variation description: Learn how interharmonics affect RMS voltage and cause flicker, crucial for power quality professionals and utility engineers. image: https://library.powermonitors.com/hubfs/AdobeStock_611850970.jpeg --- [![PMI\_Logo\_White\_Slogan](https://library.powermonitors.com/hs-fs/hubfs/Branding%20-%20Logos%20and%20Designs/PMI_Logo_White_Slogan.png?width=655&height=175&name=PMI_Logo_White_Slogan.png "PMI_Logo_White_Slogan")](https://powermonitors.com) [![PMI Logo: Tools you Need. People you Trust.](https://library.powermonitors.com/hubfs/PMI_Website/logo.svg "PMI Logo: Tools you Need. People you Trust.")](http://powermonitors.com) [![PMI Logo: Tools you Need. People you Trust.](https://library.powermonitors.com/hubfs/PMI_Website/logo.svg "PMI Logo: Tools you Need. 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Because their frequencies do not “fit” neatly into one cycle, they create low-frequency envelopes that make root-mean-square (RMS) voltage swing within a single cycle and from cycle to cycle. The paper walks through a concise mathematical derivation showing how any pair of sine components produces new sum- and difference-frequency terms in the RMS calculation, then demonstrates the practical impact with a 175 Hz component riding on the line. In the worked example, that one off-frequency tone magnifies into a 5 Hz amplitude modulation large enough to push lighting past the irritability threshold of IEEE Std 141—often a recipe for customer complaints, flicker reports, and equipment misoperation. In [PQ Canvass](https://info.powermonitors.com/pq-canvass-intro), interharmonic-aware RMS views surface low-frequency modulation for rapid field triage and evidence collection. **Key topics include:** \- HRMS Effects \- Deriving the RMS-Variation Formula \- Worked Example: 175 Hz Injection and Flicker Risk **Why utilities should care:** Light flicker is one of the most visible—and most reported—power-quality issues. The analysis in this white paper equips engineers with a clear, physics-based explanation of how seemingly small interharmonic sources such as drives, arc furnaces, or inverter-based resources can destabilize RMS readings, trip sensitive loads, and trigger costly customer claims. By understanding the math, utilities can set monitoring filters correctly, pinpoint culpable equipment faster, and justify mitigation investments with hard numbers instead of guesswork. In short, mastering interharmonics helps protect grid reliability, safeguard revenue, and strengthen customer trust. In PQ Canvass, engineers correlate HRMS swings to likely sources, flag events near IEEE flicker limits, and capture pre/post waveforms for mitigation—accelerating resolution, targeting filters or settings, and reducing repeat truck rolls with visuals alongside stripcharts. It also preserves findings, building institutional knowledge for faster future investigations across teams. You may also enjoy...   - - - - ## Speakers ### [Alvin Rogers](https://library.powermonitors.com/interharmonics-and-rms-variation#inline-content-1speakers)[Follow me on LinkedIn](https://www.linkedin.com/apex-alvinrogers) Director of Sales Omnicorp Alvin Rogers Director of Sales Omnicorp About Alvin Rogers Alvin Rogers is a highly accomplished and sought-after speaker, renowned for their expertise and captivating stage presence. With a diverse background in \[relevant field or industry\], they bring a wealth of knowledge and experience to every speaking engagement. Their dynamic and engaging style seamlessly combines powerful storytelling with actionable insights, leaving audiences inspired and equipped with practical strategies for success. Alvin has delivered impactful keynote addresses at prestigious conferences and corporate events worldwide, consistently receiving rave reviews for their ability to connect with and energize audiences. Whether addressing topics such as \[specific areas of expertise\], leadership, or innovation, Alvin is dedicated to empowering individuals and organizations to reach their full potential. [LinkedIn](https://www.linkedin.com/apex-alvinrogers) [Facebook](https://www.facebook.com/apex-alvinrogers) [Instagram](https://www.instagram.com/apex-alvinrogers) [Twitter](https://www.twitter.com/apex-alvinrogers) ### [Lisa Smith](https://library.powermonitors.com/interharmonics-and-rms-variation#inline-content-2speakers)[Follow me on LinkedIn](https://www.linkedin.com/apex-lisasmith) Creative Director Megacorp Lisa Smith Creative Director Megacorp About Lisa Smith Lisa Smith is a highly accomplished and sought-after speaker, renowned for their expertise and captivating stage presence. With a diverse background in \[relevant field or industry\], they bring a wealth of knowledge and experience to every speaking engagement. Their dynamic and engaging style seamlessly combines powerful storytelling with actionable insights, leaving audiences inspired and equipped with practical strategies for success. Lisa has delivered impactful keynote addresses at prestigious conferences and corporate events worldwide, consistently receiving rave reviews for their ability to connect with and energize audiences. Whether addressing topics such as \[specific areas of expertise\], leadership, or innovation, Lisa is dedicated to empowering individuals and organizations to reach their full potential. [LinkedIn](https://www.linkedin.com/apex-lisasmith) [Facebook](https://www.facebook.com/apex-lisasmith) [Instagram](https://www.instagram.com/apex-lisasmith) [Twitter](https://www.twitter.com/apex-lisasmith) ### [James McGiven](https://library.powermonitors.com/interharmonics-and-rms-variation#inline-content-3speakers)[Follow me on LinkedIn](https://www.linkedin.com/apex-jamesmcgiven) President Minicorp James McGiven President Minicorp About James McGiven James McGiven is a highly accomplished and sought-after speaker, renowned for their expertise and captivating stage presence. With a diverse background in \[relevant field or industry\], they bring a wealth of knowledge and experience to every speaking engagement. Their dynamic and engaging style seamlessly combines powerful storytelling with actionable insights, leaving audiences inspired and equipped with practical strategies for success. James has delivered impactful keynote addresses at prestigious conferences and corporate events worldwide, consistently receiving rave reviews for their ability to connect with and energize audiences. Whether addressing topics such as \[specific areas of expertise\], leadership, or innovation, James is dedicated to empowering individuals and organizations to reach their full potential. 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